A gasoline internal combustion engine typically takes in the air and fuel mixture, which is often referred to as charge, needed for driving the engine via the negative pressure generated during the intake strokes. An engine with larger cylinders can take in more charge and, therefore, generate more power. One approach for increasing the engine power without increasing the engine size and weight is using a gas compressor in the intake track of the engine to compress the intake air above atmospheric pressure. The gas compressor forces more charge into the engine cylinders, thereby increasing the volumetric efficiency of the engine beyond that of a normally aspired engines without the gas compressor.
The intake gas compressor is generally referred to as a supercharger. A supercharger typically includes an air inlet at the top. A compressor is located directly below the air inlet and compresses the air flowing from the air inlet. The compressed air flows through an intercooler at the bottom of the supercharger. The cooled and boosted air is fed into the engine cylinders via the engine intake manifold runners.
An intake gas compressor can be exhaust gas driven or mechanically driven. An exhaust gas driven intake gas compressor is also referred to as a turbo supercharger or a turbocharger. A mechanically driven intake gas compressor is conventionally referred to as a supercharger and is mechanically coupled to the engine crankshaft by a belt, a chain, or a gearbox. A turbocharger is generally smaller than a mechanically driven supercharger. However, the turbo lag associated with a turbocharger often results in less than desirable driving experience, especially in high performance sports cars.
Sports car enthusiasts often buy mass produced cars with a normally aspired engines and have after market superchargers installed to improve the performance of the cars. A specialty vehicle manufacturer may produce high performance sports cars by installing superchargers on normally aspired stock cars made by major automobile manufacturers. Mass produced normally aspired cars, especially compact cars, usually have very limited space in the engine bays to accommodate additional components such as superchargers.
An engine hood scoop can provide the extra space for a supercharger. However, the hood scoop deteriorates the aerodynamic characters of the car, resulting in poorer performance, lower fuel efficiency, and more wind noise. In order to fit a supercharger under the engine hood without a hood scoop, the supercharger may be installed in the valley between the engine heads of a V-engine to lower its profile. Such a supercharger arrangement requires the engine intake runners to run from the intercooler at the bottom of the supercharger located in the valley of the V-engine up to the engine heads. As the engine intake valves of a V-engine are located at the top of the engine heads, the runners include at least two sharp bends, one near the bottom of the supercharger and another near the engine heads. Sharp bends in the runners restrict the charge flow and deteriorate the engine performance. Furthermore, it will increase the pressure and temperature of the charge. High pressure and high temperature charge increases likelihood of engine detonation, thereby requiring high octane fuel and negatively impacting the engine life. High temperature charge also decreases the thermal efficiency of the engine.
Accordingly, it would advantageous to have a low profile intake gas compressor, or supercharger, that can fit under an engine hood without the hood scoop. It is desirable for the supercharger to have a large airflow to improve the volumetric efficiency of the engine. It is also desirable for the supercharger to have a low boost pressure to minimize its impact on the engine life. In addition, it is desirable for the supercharger to force a low temperature charge into the engine to improve the engine's efficiency, avoid detonation, and allow the engine to run on low octane fuels. It is of further advantage for the supercharger to be simple, inexpensive, and reliable.